The need to perform work at an elevated place has given rise to a substantial number of devices by which one can place a tool at an elevated position to be controlled from a remote point or, conversely, to place himself at the elevated position where the work must be done. It has become common to employ telescoping structures, articulated arms, scissors mechanisms, or combinations of those, and to mount them on a transporting vehicle. If the transporting vehicle is sufficiently lightweight, for whatever reason, counterweighting may be required. If the transporting vehicle must be made small so that it can maneuver in small space, then movement of the counterweight may be required. If the platform carrier is to be rotated relative to the transporter so that it can be extended in different directions relative to the transporter, the system for relating counterweight position to transporter position, and working height and degree of lateral extension, tends to become very complex. Further complexity is introduced into the mechanism and controls when the work station at the end of the boom or scissor must be maintained level. That is especially true when the operator rides at the end of the boom. Moreover, the requirement for safety in apparatus of this kind usually introduces even further complexity.